Precipitation of magnesium aluminum spinel from alumina-matrix solid solution: I, fundamental concept and precipitation behavior

Al2O3 ceramics with magnesium aluminum spinel dispersion particulates were produced by a precipitation treatment of Al2O3-matrix solid solution, (Al1- 2x,Ti-x,Mg-x)(2)O-3. We successfully constructed the precipitation process for synthesizing the nanocomposite, using the solubility dependence of tita nium and magnesium in Al2O3 on the valence of titanium. Changing of the val ence of titanium from 4+ to 3+ was accomplished by controlling the heating atmosphere, and, thereby, magnesium precipitation was promoted. The precipi tation behavior was characterized using X-ray diffractometry, and the micro structure was observed using transmission electron microscopy, We confirmed that magnesium aluminum spinel nanosized particulate were precipitated in the Al2O3 grain.